The present invention relates broadly to aircraft engine combustor systems, and in particular to a dilution air dispensing apparatus for a double dome engine combustor.
The state of the art of double dome combustor apparatus is well represented and alleviated to some degree by the prior art apparatus and approaches which are contained in the following U.S. Patents:
U.S. patent application Ser. No. 2,606,421 issued to Goddard on Aug. 12, 1952; PA1 U.S. patent application Ser. No. 3,306,333 issued to Mock on Feb. 28, 1967; PA1 U.S. patent application Ser. No. 3,820,324 issued to Grindley et al on June 28, 1974 ; PA1 U.S. patent application Ser. No. 3,851,465 issued to Verdouw on Dec. 3, 1974; PA1 U.S. patent application Ser. No. 4,113,425 issued to von Linde et al on Sept. 12, 1978; PA1 U.S. patent application Ser. No. 4,173,118 issued to Kawaguchi on Nov. 6, 1979; PA1 U.S. patent application Ser. No. 4,195,475 issued to Verdouw on Apr. 1, 1980; and PA1 U.S. patent application Ser. No. 4,237,694 issued to Wood et al on Dec. 9, 1980.
Kawaguchi patent discloses a fuel combustion cylinder having a double concentric combustion cylinder which includes a rich mixture zone, a lean mixture zone and a dilution zone.
Mock patent is directed to a combustor of the flame tube type and toroidal or smoke ring type of gas circulation in the primary zone.
Wood et al patent describes a combustor for a gas turbine engine which has a central duct partially surrounded by an annular duct. Each duct has an array of swirl vanes at their upstream ends and fuel inlet apertures are located downstream of the respective arrays of swirl vanes.
Verdouw, Grindley et al, von Linde et al, Verdouw and Goddard patents provide additional background information on the state of the field of art.
In the prior art, designers of advanced combustor engines were striving to reduce the combustor length as one of several means for reducing engine length and weight. The double dome combustor had been introduced in advanced designs as a means of reducing combustor length while meeting other important design criteria. However, preliminary studies have indicated that in these short double dome combustor designs, some amount of centerbody dilution air is needed. This additional centerbody dilution air with the dilution from the combustor inner and outer walls provides cooling to the center portion of the combustor exit stream, and is also necessary to achieve the desired temperature gradient variation (profile shape) cross the combustor exit stream. The circumferential variations in temperature must also be limited. However, this condition is expected to be particularly difficult due to the shortness of the combustor and the very limited length which is available for mixing between the location where dilution air is admitted, and the combustor exit. At some conditions, it may also be necessary to operate with fuel and combustion in only one dome. This operation would result in a very poor profile shape, which would be detrimental to combustor and turbine efficiencies. To a lesser degree, the profile and pattern factor will be sensitive to the control tolerance in setting and holding of particular fuel flow splits to the two domes.